py3versions: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/py3versions - from package: python3-minimal

You may install the required package with command apt-get install {package}

Error in other languages:
py3versions: bevel nie gevind nie
py3versions: comandă negăsită
py3versions: comando não encontrado
py3versions: commande introuvable
py3versions: command not found
py3versions: käsku ei ole
py3versions: không tìm thấy lệnh
py3versions: komanda nerasta
py3versions: Kommando nicht gefunden.
py3versions: kommandot finns inte
py3versions: komut yok
py3versions: nie znaleziono polecenia
py3versions: níor aimsíodh an t-ordú
py3versions: no se encontró la orden
py3versions: no s'ha trobat l'ordre
py3versions: opdracht niet gevonden
py3versions: parancs nem található
py3versions: perintah tidak ditemukan
py3versions: príkaz nenájdený
py3versions: příkaz nenalezen
py3versions: команда не найдена
py3versions: командата не е открита
py3versions: 命令找不到
py3versions: コマンドが見つかりません